Double outlet ventricle

Connections of the great arteries to the ventricles

The aorta is either to the right of and anterior to the pulmonary trunk, or side-by-side with the aorta to the right. Each great artery arises above a conus that prevents fibrous continuity with atrioventricular valve tissue, but conal attenuation occasionally permits fibrous continuity. When each great artery is equipped with a separate conus, and both great arteries arise exclusively from the right ventricle, the term double outlet right ventricle is not disputed. However, the appropriate terminology for hearts with a biventricular great arterial valve is unresolved.

Double outlet right ventricle with a subaortic ventricular septal defect, pulmonary stenosis, and an aortic override greater than 50% resembles Fallot’s tetralogy ( Box 16.2 , see Chapter 15 ). Double outlet right ventricle with a subpulmonary ventricular septal defect and a posterior non-border forming biventricular pulmonary trunk resembles complete transposition of the great arteries (see Box 16.2 ; see Chapter 24 ), and carries a high likelihood of unusual coronary artery morphology, significantly impacting resulting mortality. It has been proposed that double outlet right ventricle, Fallot’s tetralogy, and complete transposition represent a spectrum of anomalies resulting from embryonic arrest of the normal rotation of the junction of the outflow tract and the great arteries. In 1949, Taussig and Bing published a case of complete transposition of the aorta and levoposition of the pulmonary artery which arose chiefly from the right ventricle (see later section).

Relationship of the ventricular septal defect to the great arteries

A ventricular septal defect is usually subaortic or subpulmonary and provides the left ventricle with its only outlet ( Fig. 16.1 ). Less often, the defect is committed to both great arteries, or the ventricular septum is intact (see Box 16.1 ). ^{, ,} Rarely, the defect is in muscular or inlet septum, and is therefore not committed to either great artery. ^,

The location of the ventricular septal defect is the major determinant of intracardiac streaming. When the defect is committed to the aorta, blood flow is preferentially channeled into the aorta (see Fig. 16.1 A). Streaming is secondarily influenced by pulmonary vascular resistance and pulmonary stenosis. In the Taussig and Bing anomaly (see earlier), which constitutes less than 10% of cases of double outlet right ventricle, the aorta arises completely from the right ventricle, a non-restrictive ventricular septal defect is subpulmonary, and the pulmonary trunk is biventricular, although principally in the right ventricle. Left ventricular blood preferentially enters the pulmonary artery through the subpulmonary ventricular septal defect (see Figs. 16.1 D and 16.2 ; Videos 16.1 and 16.2 ). ^{, , ,}

Obstruction to ventricular outflow

Pulmonary stenosis occurs in 40% to 70% of cases of double outlet right ventricle with subaortic ventricular septal defect (see Fig. 16.1 C), ^, and is represented by an underdeveloped subpulmonary conus or by a stenotic bicuspid pulmonary valve. A subpulmonary ventricular septal defect is rarely accompanied by pulmonary stenosis. When there is pulmonary atresia ( Figs. 16.3 and 16.4 ), the right ventricle has a single functional outlet—the aorta—so double outlet then refers to ventriculo-arterial alignment ( Videos 16.3 , 16.4 and 16.5 ).

A non-restrictive ventricular septal defect is physiologically advantageous because it provides the left ventricle with an unobstructed exit. An inherently restrictive subaortic ventricular septal defect or a spontaneous decrease in size are forms of subaortic stenosis. The decrease in size may culminate in complete closure, ^, or rarely, the ventricular septum is congenitally intact, and the left ventricle is hypoplastic. ^, Aortic stenosis can also be caused by an underdeveloped subaortic infundibulum, which occurs in about 50% of cases with a subaortic ventricular septal defect.

Nearly one-third of patients with straddling atrioventricular valves (biventricular insertion of chordae tendineae) have a double outlet right ventricle ( Fig. 16.5 ; Videos 16.6 and 16.7 ). The straddle involves the right-sided or left-sided portion of the atrioventricular valve. Overriding refers to biventricular commitment of the atrioventricular annulus, which is not a feature of double outlet right ventricle.

The atrioventricular node is normally located, and the conduction system penetrates the right side of the central fibrous body (see Electrocardiogram). The location of the atrioventricular bundle is related to the ventricular septal defect as in isolated ventricular septal defect (see Chapter 14 ).

The classification of double outlet right ventricle in Box 16.1 is based on anatomic faults that are principally responsible for the physiologic derangements and clinical expressions of a subaortic or subpulmonary ventricular septal defect, and from the absence or presence of pulmonary stenosis or pulmonary vascular disease.

Double outlet right ventricle with subaortic ventricular septal defect

The clinical manifestations closely resemble isolated non-restrictive perimembranous ventricular septal defect (see Fig. 16.1 and Box 16.2 ). Male/female ratio is estimated at 1.7:1. A large kindred included a second cousin with double outlet right ventricle, a first cousin with complete transposition of the great arteries, and two siblings with truncus arteriosus.